1. Field of the Invention
The present invention relates to epoxidized terpolymers and functional derivatives obtained therefrom and their use in lubricant compositions, for example, as sludge dispersants and viscosity index improvers. More particularly, the invention is directed to epoxidized terpolymers of ethylene, C.sub.3 -C.sub.8 .alpha. olefins and non-conjugated dienes in which the chain of carbon atoms forming the terpolymer backbone is essentially saturated and any substantial unsaturation in the terpolymer, prior to epoxidation, is in an alkylene radical pendant to the backbone or is pendant to or part of a cyclic structure attached to the backbone. The epoxidized terpolymer may be further reacted with a functional reagent which is herein defined as a reagent having a replaceable hydrogen which will react with an oxirane in the presence of an acidic or basic catalyst to form a functional adduct. The oil-soluble epoxidized terpolymers or its functional adducts are useful as additives for lubricants, such as sludge dispersants and viscosity index improvers, and as sludge dispersants in mineral oil fuels, e.g., distillate fuel oil and gasoline.
2. Description of the Prior Art
Epoxidation of polymers of butadiene and copolymers of butadiene and styrene, in each instance of which a preponderant proportion of the unsaturation in the polymers is located in the chain backbone, has been described in U.S. Pat. No. 2,829,135 and in British Pat. Nos. 774,752 and 774,765. The resinous products obtained were useful in the formulation of surface coatings.
U.S. Pat. No. 3,388,067 is of interest in demonstrating the improvements of the present invention over the prior art. This patent describes the oxidation, preferably in the presence of a free-radical initiator, of an essentially saturated copolymer of ethylene and propylene at tertiary hydrogen sites located on the polymer backbone chain. Cleavage of the polymer chain occurs with the formation of hydroperoxidized segments of lower molecular weight polymer. Subsequent reduction of the hydroperoxidized segments yields a polymer hydroxylated on the backbone chain, useful as a viscosity index improver.